Help with solar tracker

Discussion in 'The Projects Forum' started by electronicsnewbie, Jan 17, 2010.

  1. electronicsnewbie

    Thread Starter New Member

    Dec 7, 2009
    10
    0
    I have this circuit, which works for about an hour and the dies every time I don't know why. When it dies, I have to completely rebuild it with new components to get it to work I designed it myself, which is probably why it doesn't work for long ;)

    Basically how it's supposed to work is there are two solar panels (2v Calculator panels) that are used to sense where the sun is. One of them is centered on the solar panel and has a shroud around it which stops the motor when the panel is pointing directly at the sun. By default the motor will go one way until the right hand solar panel is centered on the sun, if the sun is on the other side it powers the other solar panel which reverses the motor direction. There is another circuit (not shown) that turns off this circuit when there is not enough sun, which works.

    Anyway it works, but it keeps dieing after a while and I don't know why, it doesn't get hot (not even warm). Basically when it dies it doesn't respond in anyway to the solar panels. The solar panels are 2V and put out around 15ma short circuit. I forgot to put it on my circuit but the top line is connected to +12v (car battery). I think my resistor values may be wrong.

    I also built this circuit with 1K variable resistors in series with the solar panels in case they were providing too much current and killing the transistors ? I'm using two SPDT relays in place of the DPDT, the coils need 12V and around 50ma each.

    [​IMG]
    I hope my hand drawn schematic makes sense.

    Any help would be appreciated.
     
  2. Bernard

    AAC Fanatic!

    Aug 7, 2008
    4,176
    397
    Add 2k ohm resistors in series with the three bases on left side of drawing.
     
  3. SgtWookie

    Expert

    Jul 17, 2007
    22,182
    1,728
    Actually, just the bases that are connected to the solar cells need current limiting resistors.

    Somewhere between 470 and 680 Ohms should work OK.
     
  4. electronicsnewbie

    Thread Starter New Member

    Dec 7, 2009
    10
    0
    Thanks, I'll try that! Circuit attempt #4 coming soon :)
     
  5. Art

    Distinguished Member

    Sep 10, 2007
    785
    61
    Could you post better pics or video when it's working?
    Of the actual device I mean.
     
  6. SgtWookie

    Expert

    Jul 17, 2007
    22,182
    1,728
    Actually, you are using some of the transistors as voltage followers. They will dissipate a lot of power that way, causing internal heating - and they will probably burn up due to that internal heating.

    Your schematic is very hard to read. Could you possibly post a smaller, better-focused image that was taken with better lighting? I know, it's hard to do that.
     
  7. Externet

    AAC Fanatic!

    Nov 29, 2005
    763
    57
    Relays on emitters ?
     
  8. Bernard

    AAC Fanatic!

    Aug 7, 2008
    4,176
    397
    Nothing wrong with emitter followers for driving relays, but would drive them a little harder by replacing 3.9k's with 1k to 2.2ks, disipation should be about 50 mWs.
     
Loading...